A quick fix? oil be the judge of that

[SixasStandard]

Hello all,

Whilst doing my usual trawl of the internet for all things Triumph (and yes......before anyone says it..... I know I should get a life) I stumbled upon a page documenting a quick fix for low oil pressure on Triumph six cylinder engines, and just wanted to get the opinions of other Forum members. It is a very simple mod, and just involves unscrewing the 7/8" hex housing of the oil pressure relief valve, popping the unit out and adding a flat washer between the spring and the plunger on the centre spindle. This effectively increases the spring pressure on the plunger, and raises the oil pressure before the pressure relief valve kicks in.

Any thoughts?

Ian   

[Nigel Clark]

The short answer is NO.

If the oil pressure is low, it's because the oil pump and/or bearings are worn. The pressure relief valve is a spring loaded valve. As engine revs rise, the oil pump is running faster and trying to deliver more oil, potentially causing excessive pressure and leaks. The spring on the pressure relief valve allows its piston to rise, so some of the oil delivered from the fast-spinning pump is diverted back to the sump, instead of following the usual path via the oil galleries to the crankshaft and cam bearings. This controlled return of excess oil to the sump prevents the pressure rising too high.

Packing the pressure relief valve spring with washers will delay the point at which excess oil pressure is vented back to the sump, so at high rpm the oil pressure may be too high. This becomes more of a problem when the engine is cold and the oil is thick.

The Triumph engineers did a good job when they designed our engines' lubrication system. My advice is don't try to adjust the relief valve and don't add one of those external rocker oil feed pipes either. The only modifications worth fitting on the lubrication system are a spin off filter conversion for six cylinder engines, and possibly an oil cooler with thermostat for highly tuned engines that are regularly driven hard. Other than that, keeping the lubrication system standard is best, with regular oil and filter changes.

Nigel

[johny]

yes typically a worn engine will show low oil pressure (with possibly the warning light coming on) at idle when hot and especially with poor quality/high mileage oil. At that point you could blank off the relief valve completely and it still wouldnt improve things!

[dougbgt6]

Rimmers sell ordinary and uprated pressure relief springs. Knowing what we know, the purpose of the uprated spring is not entirely clear, unless you're hoping to sell the car and washers would be a dead give away?

Doug

[Pete Lewis]

i agree if the pressure is low upping the PRV spring has no effect unless the spring  is stuffed ,  thats most unlikely 

if some debris has got under the seat of the valve then you get low pressure this is just a remove clean and refit ,  plonkers adding washers is 

just another myth you dont need   low pressure is down to worn  bearings/pump and/or cheap oil 

the prv piston is a simple flat faced seating  generally   very reliable 

sorry this is a typical treat the wrong end of a problem,problem 

[SixasStandard]

I can't help but wonder though if there's a case to be made that the PRV spring might degrade over time due to the temperatures that it is continually exposed to. Let's face it, with an engine like mine that has 114k miles on it (and never been apart) that spring has seen quite a bit of service, and might not be operating to OE spec.  The most obvious diagnosis for low oil pressure is certainly going to be the 'usual suspects' already highlighted, but doesn't that relate more to the pressure at hot tick over rather than the pressure at the upper end of the rev range? At tick over the pressure should be about 25lbs to 30lbs shouldn't it? anything lower than 20lbs should be an indicator of something untoward, and the PRV spring won't be an issue at those pressures whatever its condition. But if the PRV spring isn't working to spec then that could result in a lower pressure than necessary at higher revs if the PRV is operating earlier than it should due to a weak spring.

I've just nipped out to the garage and performed this mod as an experiment to see what would happen. It takes minutes to do, so why not??  Now, referring back to my thread earlier this week regarding oil filters and positioning of the spin off filter adaptor, that has provided me with some baseline figures to act as a comparison. With the previous (standard) set up I was getting 25lbs at hot tick over, and 50lbs at 2000rpm............after adding a single washer to the PRV I'm now still getting 25lbs at hot tick over, but the 2000rpm reading has increased to 60lbs. That says to me that the PRV spring isn't working to original spec, as Triumph's own figures specified up to 60lbs at 2000rpm hot, so if my engine's achieving that now when it wasn't before then it can only be the washer compensating for the reduction in spring rate. Let's also remember that the Triumph figures are based on a new engine, so surely with older engines like mine isn't a boost to the oil pressure at higher revs beneficial? as long as it doesn't take the level outside OE specs? 

Ian      

[Pete Lewis]

the spec is 40 to 60 , so quite a range 

yes wear and tear on the spring is an obvious but not for idle pressures   as you have found 

had a ramble but not found the spring spec   to test one 

pete

[johny]

Did you check the spring complies the WSM specification (free length and load at fitted length)? If these are correct and the valve seats well then the system will work as Triumph intended and no washers needed...

[Pete Lewis]

johny   if you find the spec somewhere , that would be good  , i cant unearth it from my collection of WSM 

part number  131535   used on every engine from 948 to 2500 and  less than  £2 its not worth messing with 

Pete

[68vitesse]

From Vitesse and GT6 WSM.

Regards

Paul

[johny]

my VitesseGT6 manual says 1.55" free length, 1.25" fitted giving a load of 14.5lb at that point👍

[SixasStandard]

45 minutes ago, johny said:

Did you check the spring complies the WSM specification (free length and load at fitted length)? If these are correct and the valve seats well then the system will work as Triumph intended and no washers needed...

I'll take the spring out and measure it, which will indicate whether it's the right Triumph part, or else some random spring that has been fitted by a PO. Assuming that it is the correct part, then my previous comments still apply........i.e. that the spring can degrade over time, and that lower oil pressure at higher revs can be the result of a faulty PRV spring, not simply wear to the main moving components or cheap oil. As Pete has pointed out there is also the possibility of debris in the oil fouling the PRV piston, by which I'm assuming that he means metal fragments from the big end shells, so perhaps I'll fit a magnet to the oil sump plug next time I do an oil change, just to be on the safe side!

Ian   

[johny]

try also to measure the weight needed to compress it to the fitted length if possible and then you´ll know you have a 100% correct set up so will be able to sleep easier at night🤣

[SixasStandard]

51 minutes ago, johny said:

try also to measure the weight needed to compress it to the fitted length if possible and then you´ll know you have a 100% correct set up so will be able to sleep easier at night🤣

Sorry Johny I didn't pick up your reply until after getting back from the garage (I've never had the bonnet up and down so many times in a single day!!). Anyway........interesting findings!!

The spring definitely looks OE, but when measured with a vernier turned out to have a free length of 1.504" (38.2mm) rather than the OE spec 1.55" (39.37mm), so not sure whether that's due to an incorrect part.......or the aforementioned heat degradation. Anyway, whatever the truth of it the fact remains that the spring is too short. Interestingly the washer I've added is 1.6mm thick, so now theoretically giving me 39.8mm spring length, so only 0.43mm over spec!!  Just goes to prove that it's worth the 5 minutes it takes to pop this litter sucker out and have a quick measure up if your engines running a bit low on pressure at higher revs. Anyway, all's well that ends well, and as I'm now happy with the hot oil pressure at 2000rpm I'll leave the washer in............sorry if that makes me a 'plonker' Pete!!

Ian 

[Pete Lewis]

good  i had a good scout through but didnt spot the spec ( spec savers is on the to do list )

 plonkers only apply when its used for the wrong reasons   ,  youve done your homework  got a solution      so  gold star but the governments  algorithm  reduces you to ......plonker 

pete

[SixasStandard]

12 minutes ago, Pete Lewis said:

good  i had a good scout through but didnt spot the spec ( spec savers is on the to do list )

 plonkers only apply when its used for the wrong reasons   ,  youve done your homework  got a solution      so  gold star but the governments  algorithm  reduces you to ......plonker 

pete

I intend to appeal the decision.......I'm holding out for 'Plonker**' (at least I won't have to pay the 100 quid now).

Ian

[Pete Lewis]

A+   

pete

[Clive]

Better than adding washers would be a correct new spring. However, I am increasingly disillusioned with the quality of supplied parts (new steering UJ has twice the play of the one I took out, not impressed. Sadly I can't remember the supplier as bought a few years ago.) So reusing the old spring is fine. Just remember it controls the maximum pressure, as you have found out. Also worth remembering pressure is not the be-all, you need good flow of oil too. 

Quality oil appropriate to your use, and a crank/bearings that re not excessively worn are the things that matter most. 40psi hot/running is enough to keep an engine happy providing no excessive wear.

[SixasStandard]

2 hours ago, clive said:

Better than adding washers would be a correct new spring. However, I am increasingly disillusioned with the quality of supplied parts (new steering UJ has twice the play of the one I took out, not impressed. Sadly I can't remember the supplier as bought a few years ago.) So reusing the old spring is fine. Just remember it controls the maximum pressure, as you have found out. Also worth remembering pressure is not the be-all, you need good flow of oil too. 

Quality oil appropriate to your use, and a crank/bearings that re not excessively worn are the things that matter most. 40psi hot/running is enough to keep an engine happy providing no excessive wear.

I share your reservations about the quality of many new parts Clive, it really is a lottery.........so in this case I'll be sticking with the current solution of the OE spring with the washer. I take your point regarding quality of the oil, and at the next oil change will be using Classic Oils - Heritage 20W50.

I have to assume that my engine, with its high mileage, is in the 'well worn' category.......although saying that it isn't particularly noisy and doesn't burn oil. Bearing this in mind I think that the modest increase in oil pressure that I'm seeing at higher revs will be beneficial for my engine, and has made the exercise worthwhile. 

Ian

[Peter Truman]

I agree with you Ian it is a PRV so if it blows off pressure to the sump by opening up at 50psi it will deliver more flow to the oil ways and bearings at 60psi when it opens within the limitations of the oil way "coeff of friction", the result of the increased pressure could be more leakage than usual for a Triumph engine from the external extremities.

My never rebuilt Mk2 Vitesse engine develops nearly 100psi on startup and around 80 normal running dropping to around 65/70 on a hot summers day, idle >25 normally maybe around 20 on a hot day. For the first 30 years I always worried that there was a restriction in the oil passage ways, for the next 20 years after that I reckoned as it had lasted that long (now 52years) whatever caused the high pressures wasn't causing any long term effect!

I did remove and clean the PRV once around 1972 when at 4:30AM driving my wife to catch an early overseas flight I noticed the running pressure was only 40psi, at Middleton St George Airport I removed the valve checked all was clean refitted and all OK back to around 70+psi as it has been for the last 48 years since! What caused it maybe the valve dislodged sideways a little a bit of debris I'll never know. I'll check the spring length and let you know, it could be the depth of the valve seat in the block varies between engines which increases or decreases the spring tension and seat pressure, there's tolerances everywhere! I've tried different PRV  cap nuts from other engines which hasn't made any difference to the pressures.

[Clive]

10 hours ago, SixasStandard said:

I share your reservations about the quality of many new parts Clive, it really is a lottery.........so in this case I'll be sticking with the current solution of the OE spring with the washer. I take your point regarding quality of the oil, and at the next oil change will be using Classic Oils - Heritage 20W50.

I have to assume that my engine, with its high mileage, is in the 'well worn' category.......although saying that it isn't particularly noisy and doesn't burn oil. Bearing this in mind I think that the modest increase in oil pressure that I'm seeing at higher revs will be beneficial for my engine, and has made the exercise worthwhile. 

Ian

Ian, it is VERY possible, or even probable, that the engine has had some work during its lifetime. About half the engines I have taken apart have, most of the ones I stripped 20 years ago were std size, but the last half dozen (Triumph) engines have all been rebored and cranks ground. At least once....

The Classic Oils stuff seems to be a sound choice for general use. Excellent value too. 

[SixasStandard]

42 minutes ago, clive said:

Ian, it is VERY possible, or even probable, that the engine has had some work during its lifetime. About half the engines I have taken apart have, most of the ones I stripped 20 years ago were std size, but the last half dozen (Triumph) engines have all been rebored and cranks ground. At least once....

The Classic Oils stuff seems to be a sound choice for general use. Excellent value too. 

Hello Clive,

Remarkably I have a MASSIVE history file with my car, including all of the MOTs back to 1978, the original service book with all of the work undertaken up to 60k, and then all of the garage bills, receipts, etc. for any work since that time. One of the first things I did was to go through every piece of paper and file it by decade in two file folders. The first owner was Sir Kelvin Spencer, and as an engineer himself he had the car diligently maintained and was meticulous with his record keeping. The second owner had the car for 37 years, and like his predecessor kept all of the paperwork for any work conducted. The third owner only had the car for three years, wasn't mechanically inclined and used the car very sparingly. So as you can see there can't be many cars out there with such a complete history, and I now intend to carry on with this fastidious care and record keeping. The only time the engine has been apart according to the records was for a de-coke back in the 1970s. Having contacted the second owner he confirms that the engine was never apart in his ownership. 

Ian  

[Peter Truman]

Ian as I said I'd measure my spring ie original 52 years old it is 1.51in free length less than the WSM of 1.55in and I run at over 70psi hot and 2000rpm, I won't be replacing or assisting the spring.

Interestingly in the early 60's dads merc 300SEL OE oil pressure gauge had a max full scale of 4.5kg/cm2 (around 70psi), and when running always ran at full scale and only dropped onto the scale at idle, so I assume from that that higher pressures were irrelevant and running pressures of 50 to 60psi were good. In reality the rough accuracy of our oil pressure gauges mean they are only indicators that everything is OK normal if 50 to 60 or there is potentially an issue if dropping to under 40, if your not consuming oil or blowing smoke then alls good!

[Colin Lindsay]

1 hour ago, Peter Truman said:

Interestingly in the early 60's dads merc 300SEL OE oil pressure gauge had a max full scale of 4.5kg/cm2 (around 70psi), and when running always ran at full scale and only dropped onto the scale at idle, so I assume from that that higher pressures were irrelevant and running pressures of 50 to 60psi were good. In reality the rough accuracy of our oil pressure gauges mean they are only indicators that everything is OK normal if 50 to 60 or there is potentially an issue if dropping to under 40, if your not consuming oil or blowing smoke then alls good!

I have a Smiths oil pressure gauge fitted; came from some unknown British Classic but the needles pointed in the same downwards direction as the other gauges so I fitted it.

It goes to about 100 on startup, sits at about 80 in normal driving and when very hot drops to about 50 on idle. As you say, Peter, I just use it as an indicator; if it drops to zero I'll panic but otherwise it's just there to match the other gauges and was never calibrated nor intended as an exact guide to oil pressure.

[SixasStandard]

1 hour ago, Peter Truman said:

Ian as I said I'd measure my spring ie original 52 years old it is 1.51in free length less than the WSM of 1.55in and I run at over 70psi hot and 2000rpm, I won't be replacing or assisting the spring.

Interestingly in the early 60's dads merc 300SEL OE oil pressure gauge had a max full scale of 4.5kg/cm2 (around 70psi), and when running always ran at full scale and only dropped onto the scale at idle, so I assume from that that higher pressures were irrelevant and running pressures of 50 to 60psi were good. In reality the rough accuracy of our oil pressure gauges mean they are only indicators that everything is OK normal if 50 to 60 or there is potentially an issue if dropping to under 40, if your not consuming oil or blowing smoke then alls good!

Hello Peter,

The varying lengths of these PRV springs suggests to me that their free length reduces over time with the effects of heat degradation, effectively reducing the piston pressure from the original spec of 14.5lbs. I just can't imagine, even given the vagaries of BL quality control in period, that these springs would have varied that much in free length as a matter of course when new. Whatever the truth of it, and factoring in the unknown quantity of my oil gauge's accuracy........my engine's working oil pressure when hot has increased in the range of 5 to 10lbs over the previous readings, so I'm happy with that, and as previously mentioned seems to indicate that the PRV was operating a bit too early. I've fitted a Smiths oil pressure gauge  that I had laying around the shed, so I suppose I shouldn't expect too much from it as far as accuracy is concerned........but the relative before and after readings do tell a credible story!!

Ian